It is known practice to dye keratin fibres, and in particular human hair, with dye compositions containing oxidation dye precursors, generally known as “oxidation bases”, in particular ortho- or para-phenylenediamines, ortho- or para-aminophenols, and heterocyclic bases.
Oxidation dye precursors are compounds that are initially uncoloured or only weakly coloured, which develop their dyeing power on the hair in the presence of oxidizing agents, leading to the formation of coloured compounds. The formation of these coloured compounds results either from an oxidative condensation of the “oxidation bases” with themselves or from an oxidative condensation of the “oxidation bases” with coloration modifiers, or “couplers”, which are generally present in the dye compositions used in oxidation dyeing and are represented more particularly by meta-phenylenediamines, meta-aminophenols and meta-diphenols, and certain heterocyclic compounds.
The variety of molecules used, which consist on the one hand of the “oxidation bases” and on the other hand of the “couplers”, allows a very wide range of colours to be obtained.
These oxidation bases and couplers are formulated in vehicles or supports allowing them to be applied to keratin fibres after mixing with an oxidizing agent.
These vehicles are generally aqueous and usually comprise one or more surfactants.
Thus, it has already been recommended to use anionic surfactants of the carboxylic acid alkyl ether type, in combination with nonionic oxyalkylenated surfactants. The said combinations produce oxidation dye compositions that have good rheological properties and generate shades with very good dyeing properties. However, it has been observed that when oxidation dyes are used in hydrochloride or sulphate form, such combinations of surfactants lead to heterogeneous, non-clear compositions.